The present invention relates generally to the field of electrosurgery, and more particularly to surgical devices and methods which employ high frequency electrical energy to remove fatty tissue.
Suction lipectomy, commonly known as liposuction or lipoxheresis, is a well known surgical procedure used for sculpturing or contouring the human body to increase the attractiveness of its form. In general, the procedure involves the use of a special type of curette or cannula which is coupled to an external source of suction. An incision is made in the target area and the fatty tissue is essentially vacuumed from the patient""s body. This procedures has its disadvantages, however, because the fat is relatively difficult to separate from the surrounding tissue. Such separation often causes excessive bleeding and damage to adjacent tissue or muscles. A further problem is that the surgeon must be careful not to allow the suction to remove or injure any desirable tissues, such as muscle, blood vessels, skin, subcutaneous tissues and the like. In addition, it is often difficult to maintain constant suction without stopping to clean tissue fragments from the cannula. Normally, the surgeon attempts to compensate for this problem by rapidly moving the cannula within the cavity, and even periodically withdrawing it to allow the fat to move through the cannula. This causes further trauma and collateral damage to surrounding muscle, tissue and other body structures.
In an effort to resolve some of the drawbacks with conventional liposuction, ultrasonic probes for vibrating and aspirating adipose tissue have been developed. The ultrasonic vibrations physically melt the fatty tissue so that it can be emulsified and aspirated through the probe. These ultrasonic probes have reduced the physical exertion required by the surgeon to remove fatty tissue, increased the speed of the operation and reduced the collateral damage created at the incision point. One problem with these probes, however, is excess heat generation at the distal tip of the ultrasonic probe. For example, when the probe has been inserted into the fatty tissue near the skin or the peritoneum, resistance can be met, which increases the wattage at the tip of the probe. The heat generated at the tip of the probe from the increased wattage may be in excess of the heat required for melting the fatty tissue. This excess heat results in burning of tissue, collateral damage to muscles or blood vessels and even penetration of membranes such as the skin or the peritoneum.
RF energy has also been used in liposuction procedures to remove fatty tissue. In particular, microwave and monopolar RF devices have been used to heat and soften fatty tissue so that the tissue can be more readily detached from the adjacent tissue with a suction instrument. Similar to ultrasonic energy, however, current microwave and monopolar RF devices have difficulty controlling excess heat generation at the target site, resulting in undesirable collateral tissue damage. For example, conventional electrosurgical cutting devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a xe2x80x9ccutting effectxe2x80x9d along the pathway of localized tissue heating. This cutting effect generally results in the production of smoke, or an electrosurgical plume, which can spread bacterial or viral particles from the tissue to the surgical team or to other portions of the patient""s body. In addition, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site.
Moreover, monopolar electrosurgery methods generally direct electric current along a defined path from the exposed or active electrode through the patient""s body to the return electrode, which is externally attached to a suitable location on the patient""s skin. In addition, since the defined path through the patient""s body has a relatively high electrical impedance, large voltage differences must typically be applied between the active and return electrodes to generate a current suitable for cutting or coagulation of the target tissue. This current, however, may inadvertently flow along localized pathways in the body having less impedance than the defined electrical path. This situation will substantially increase the current flowing through these paths, possibly causing damage to or destroying tissue along and surrounding this pathway.
The present invention provides systems, apparatus and methods for selectively applying electrical energy and suction to fatty or adipose tissue to remove the adipose tissue from the patient (e.g., liposuction, abdominoplasty and the like).
In one aspect of the invention, a method for removing adipose or fatty tissue underlying a patient""s epidermis in body regions, such as the abdomen, lower torso, thighs, face and neck, is disclosed This method includes positioning one or more active electrode(s) and one or more return electrode(s) in close proximity to a target region of fatty tissue. A high frequency voltage difference is applied between the active and return electrodes, and the fatty tissue or fragments of the fatty tissue are aspirated from the target region. The high frequency voltage either heats and softens or separates the fatty tissue or completely removes at least a portion of the tissue. In both embodiments, the remaining fatty tissue is more readily detached from the adjacent tissue in the absence of energy, and less mechanical force is required for removal. The bipolar configuration of the present invention controls the flow of current to the immediate region around the distal end of the probe, which minimizes tissue necrosis and the conduction of current through the patient. The residual heat from the electrical energy also provides simultaneous hemostasis of severed blood vessels, which increases visualization and improves recovery time for the patient. The techniques of the present invention produce significantly less thermal energy than many conventional techniques, such as conventional ultrasonic and RF devices, which reduces collateral tissue damage and minimizes pain and postoperative scarring.
In one embodiment, the method comprises introducing a distal end of an electrosurgical instrument, such as a probe or a catheter, to the target site, and aspirating fatty tissue from the target site through one or more aspiration lumen(s) in the instrument. High frequency voltage is applied between one or more aspiration electrode(s) coupled to the aspiration lumen(s) and one or more return electrode(s) so that an electric current flows therebetween. The high frequency voltage is sufficient to remove or at least soften a portion of the tissue before the tissue passes into the aspiration lumen(s). This partial or total ablation reduces the size of the aspirated tissue fragments to inhibit clogging of the aspiration lumen.
In an exemplary embodiment, the tissue may be removed and/or softened by an electrosurgical probe having an aspiration lumen and one or more aspiration electrode(s) to prevent clogging of the lumen. The aspiration electrode(s) are usually located near or at the distal opening of the aspiration lumen so that tissue can be partially ablated before it becomes clogged in the aspiration lumen. In some embodiments, the aspiration electrodes(s) are adjacent to the distal opening, or they may extend across the distal opening of the lumen. The latter configuration has the advantage of ensuring that the fatty tissue passing through the aspiration lumen will contact the aspiration electrode(s). In other embodiments, the aspiration electrode(s) may be positioned within the aspiration lumen just proximal of the distal opening. This embodiment has the advantage of eliminating any possibility of contact between the surrounding tissue and the return electrode. The aspiration electrode(s) may comprise a loop, a coiled structure, a hook, or any other geometry suitable for ablating the aspirated tissue. In one representative embodiment, the electrosurgical probe comprises a pair of loop electrodes disposed across the distal end of the suction lumen. A more complete description of such a device can be found in Ser. No. 09/010,382, filed Jan. 21, 1998 (attorney docket A-6), previously incorporated herein by reference.
The electrosurgical probe will preferably also include one or more ablation electrode(s) for ablating or softening fatty tissue at the target site prior to aspiration of the remaining tissue fragments from the patient""s body. Typically, the ablation electrode(s) are different from the aspiration electrode(s), although the same electrodes may serve both functions. In an exemplary embodiment, the probe includes a plurality of electrically isolated electrode terminals surrounding the distal opening of the aspiration lumen. High frequency voltage is applied between the electrode terminals and a return electrode to ablate or soften the fatty tissue at the target site. The non-ablated tissue fragments are then aspirated from the target site. Preferably, one or more of the electrode terminals are loop electrodes that extend across the distal opening of the suction lumen to ablate, or at least reduce the volume of, the tissue fragments, thereby inhibiting clogging of the lumen. The aspiration or loop electrodes may be energized with the active electrode terminal(s), or they may be isolated from the electrode terminal(s) so that the surgeon may select which electrodes are activated during the procedure.
In some embodiments, the return electrode(s) comprises an annular electrode member on the probe itself, spaced proximally from the aspiration and ablation electrodes. In these embodiments, electrically conducting fluid, such as isotonic saline, is preferably used to generate a current flow path between the aspiration and active electrode(s) and the return electrode(s). High frequency voltage is then applied between the aspiration and active electrode(s) and the return electrode(s) through the current flow path created by the electrically conducting fluid. Depending on the procedure, the electrically conductive fluid may be delivered to the target site through, for example, a fluid lumen in the probe or a separate instrument, or the fluid may already be present at the target site, as is the case in many arthroscopic procedures.
The return electrode(s) are preferably spaced from the active electrode(s) a sufficient distance to prevent arcing therebetween at the voltages suitable for tissue removal, and to prevent contact of the return electrode(s) with the target tissue. The current flow path between the active and return electrodes may be generated by directing an electrically conducting fluid along a fluid path past the return electrode and to the target site, or by locating a viscous electrically conducting fluid, such as a gel, at the target site, and submersing the active and return electrode(s) within the conductive gel. The electrically conductive fluid will be selected to have sufficient electrical conductivity to allow current to pass therethrough from the active to the return electrode, and such that the fluid ionizes into a plasma when subject to sufficient electrical energy, as discussed below. In the exemplary embodiment, the conductive fluid is isotonic saline, although other fluids may be selected, as described in co-pending Provisional Patent Application No. 60/098,122, filed Aug. 27, 1998 (attorney docket no. CB-7P), the complete disclosure of which is incorporated herein by reference.
In the exemplary embodiment, the adipose tissue is removed with molecular dissociation or disintegration processes. Conventional electrosurgery cuts through tissue by rapidly heating the tissue until cellular fluids explode, producing a cutting effect along the pathway of localized heating. The present invention volumetrically removes the tissue along the cutting pathway in a cool ablation process that minimizes thermal damage to surrounding tissue. In these processes, the high frequency voltage applied to the active electrode(s) is sufficient to vaporize an electrically conductive fluid (e.g., gel or saline) between the electrode(s) and the tissue. Within the vaporized fluid, a ionized plasma is formed and charged particles (e.g., electrons) are accelerated towards the tissue to cause the molecular breakdown or disintegration of several cell layers of the tissue. This molecular dissociation is accompanied by the volumetric removal of the tissue. The short range of the accelerated charged particles within the plasma layer confines the molecular dissociation process to the surface layer to minimize damage and necrosis to the underlying tissue. This process can be precisely controlled to effect the volumetric removal of tissue as thin as 10 to 50 microns with minimal heating of, or damage to, surrounding or underlying tissue structures. A more complete description of this phenomena is described in commonly assigned U.S. Pat. No. 5,683,366, the complete disclosure of which is incorporated herein by reference.
The present invention offers a number of advantages over current RF, ultrasonic, microwave and laser techniques for removing or softening tissue. The ability to precisely control the volumetric removal of tissue results in a field of tissue removal that is very defined, consistent and predictable. This precise heating also helps to minimize or completely eliminate damage to healthy tissue structures or nerves that are often adjacent to the target tissue. In addition, small blood vessels within the skin tissue are simultaneously cauterized and sealed as the tissue is removed to continuously maintain hemostasis during the procedure. This increases the surgeon""s field of view, and shortens the length of the procedure. Moreover, since the present invention allows for the use of electrically conductive fluid (contrary to prior art bipolar and monopolar electrosurgery techniques), isotonic saline may be used during the procedure. Saline is the preferred medium for irrigation because it has the same concentration as the body""s fluids and, therefore, is not absorbed into the body as much as other fluids.
A further understanding of the nature and advantages of the invention will become apparent by reference to the remaining portions of the specification and drawings.